Contact device



1948- E. M. GLASER ETAL 2,434,740

A D ICE Filed Feb. 17 1944 r km a m M 2 Wm W .F W k Patented Jan. 20,1948 CONTACT DEVICE Edward M. Glaser, Bellmore, and Girard S Toombs,Rockville Centre. N. Y., assignors to Square D Company, Detroit, Mich.,a corporation of Michigan Application February 17, 1944, Serial No.'522,722

1 Claim. 1

This invention relates to electrical apparatus, such as motors,generators, remote transmission units and similar devices whereinrelatively moveable contacts are necessary.

One object of this invention is .to improve the efiiciency anddependability of precision remote control devices such as are used onaircraft to transmit angular movements.

Another object is to provide an electrical contact between relativelymoving surfaces, which will not be interrupted by vibrations.

More particularly our invention relates to aso-called brush whereby thecurrent which it carries will not be interrupted under the influence ofvibration, and which will impose a minimum frictional load by reason ofitscontact.

Serious disturbances are experienced in the use of electrical apparatusof the above mentioned class where such apparatus is subject to vibration. On aircraft, for example, vibrations of various frequencies areset up by the engine and other equipment, causing contact disturbancesin electrical devices due to. the fact that contact brushes, if excitedto resonance, will periodically interrupt the circuits in which theylie. The contact interruption leads to sparking at the point ofinterrupted contact, injury to the contact surfaces by the are createdat the point of interrupted contact, static interference with radioequipment .of the aircraft, and faulty performanc'e of the electricalapparatus, such as, for example, an incorrect transmission of a primarymotion to a remote point.

The invention provides a contact device which remains in operativecontact under severe vibration and comprises a plurality of individualcon tact elements, the natural frequency of vibration of one contactelement being difierent from the natural frequency of the other.

Although the novel features, which are believed to be characteristic ofthis invention, will be particularly pointed out in the claim appendedhereto, the invention itself, its objects and advanta es, and the mannerin which it may be carried out, may be better understood by referring tothe following detailed description, taken in connection with theaccompanying drawing, forming a part thereof, in which Fig. l is a sideelevation of a contact device or brush embodying the present inventionwherein is also shown, partly broken away, a rotor;

Fig. 2 is a cross section view at AA of the contact device andcooperative parts shown in Fig. 1; and

Fig. 3 is a plan view of a blank from which a contact brush embodyingthe invention may be made.

In the following description and in the claim various details may beidentified by'specific names for convenience. These names, however, areintended to be as generic in their application as the art will permit.Like reference characters refer to like parts in the several figures ofthe drawings.

Referring to Figs. 1 and 2, a rotor ll of an electrical apparatus, whichmay be a motor, a generator or a remote transmission unit, is mounted ona shaft l2 and equipped with a rotary contact surface 13. The contactsurface I3 is shown to be in the form of a slip ring, but it will beapparent that it may also assume the form of a commutator, A contactbrush I4 is mounted on a support l5 of insulating material by screws 16and I6 passing through the base ll of the brush. A conductor I8 issoldered to a terminal 19, at 20.

The contact brush is made of resilient sheet metal and comprises twoarms 2| and 22 integral with the base l1. Each contact arm is providedwith a terminal portion 25 and 26, respectively, formed by twisting theend of each arm approximately with respect to the remainder of the arm.The edges of the twisted terminal portions rest against, and makecontact with, the slipring l3.

The effective length of the arm 2! is greater than that of the arm 22.The lengths of the arms are so selected that the natural frequency andsalient harmonics of one arm are dissimilar from the natural frequencyand salient harmonics of the other. When, therefore, vibration forcesare experienced and one arm is caused to vibrate, the other arm remainsin contact with its associated contact surface. v

Fig. 3 shows a form of blank of resilient sheet metal from which thecontact brush of Figs. 1 and 2 may be made. The blank may be stampedfrom a sheet or strip of su table resilient metal, such as Phosphorbronze or beryllium bronze of a thickness corresponding to B & S gau e38.

We have found that a brush made from such a stamping, when its arms aretwisted as shown in Figs. 1 and 2 provides adequate contact in alloperating conditions while imposing a braking load on its cooperatingsurface which is less than that of any practicable brush known to us inthe prior art.

Obviously, the present invention is not restricted to the particularembodiment herein 3 shown and described. It will be apparent from theforegoing disclosure that the contact brush may assume other forms thanillustrated in the drawings. It is, however, of primary importance ormore separate arms each of which contacts the slip ring, commutator orother surface with which it cooperates, and so that each arm shall havea different natural frequency of vibration.

What is claimed is:

A contact brush of resilient sheet metal comprising a base portionadapted to be mounted on a support and two strips extending from saidbase portion and forming contact :arms capable of vibrating relativelyto said base, the naturaloirequencies of vibration of the arms beingdissimilar, an end portion of each arm beingitwisted atsub stantiallyright angles with regard to the 'remainder o! the arm. the'twistedportionitorming contact portions.

EDWARD M. GLABER. 'GIRARD s."rooMBs.

to construct the brush so that it shall have two l 'aarauncas crrm Thefollowing references are or record in the file of this patent:

UNITED STATES PATENTS

